Abstract

Three-dimensional molecular dynamics simulations of aggregates of dust grains interacting via repulsive Yukawa forces, and subject to heating by neutrals and realistic boundary conditions, suggest that grain transport is ubiquitously anomalous for soft states at the transition between liquid and solid. These anomalies include self-similar, stretched-Gaussian, probability density distributions of grain displacements and superdiffusive displacement scaling on the short time scales for which the mean displacements are less than the interparticle distance . However, the details of the anomalous transport on these shorter time scales depend on system stiffness and confinement conditions. On time scales for which , humps can develop on the distribution at integer multiples of , an effect of cooperative hopping of grains on the lattice. Relaxation toward Gaussian displacement distributions and normal diffusion takes place on time scales for which . The simulations indicate that qualitative features previously found for hexatic states of two-dimensional aggregates by simulation and experiment are also present in three-dimensional configurations.